The synthesis of metal particles referred to herein as nanoclusters or nanoparticles has been the subject of considerable interest. Small size may be needed for effective catalysts and is usually needed for high-resolution labeling of biological samples for transmission electron microscopic (TEM) examination. Small size is also expected to be important for fluorescent tags useful for labeling non-fluorescent biomolecules (proteins, nucleic acids, for example) and their assemblies that are not naturally fluorescent. Fluorescent tags can be so large that they perturb biomolecules as the biomolecules interact with a binding partner, and tags might bleach rapidly, which can limit the time window that a molecular event for a biomolecule can be measured. Fluorescent noble metal nanoclusters (gold or silver, for example) might be better tags than those currently available because fluorescent noble metal nanoclusters can exhibit a strong, size-dependent light emission, can be very small, and can be attached to biomolecules.
Dendrimers, known also as dense star polymers, have been used as templates to prepare large non-fluorescent metal nanoclusters and nanoparticles.
Oligonucleotides, proteins, and DNA have been reported as templates to prepare fluorescent metal nanoclusters.